This invention relates to the control of automatically operated sliding doors, and more particularly to providing improved safety control for such doors to prevent door contact with persons or objects in the path of the door.
Automatically controlled power driven sliding doors are in wide use for entry into buildings, rooms, elevators and the like. The extensive use of such doors is fostered by their intrinsic utility and convenience as well as their space-saving features. Since a sliding door operates in the plane of the entrance, problems of providing additional space for a swinging door, as well as potential contact with transistors by a swinging door are avoided.
In the usual automatic sliding door installation, the opening of the door is initiated by sensors installed to monitor the approaches to the door. One method commonly used is to employ a movement detecting device such as a doppler sensor that detects the approach of transitors to initiate opening, or cycle the door to re-open it if it is in the process of closing. The door power controls are equipped with time delays that permit transit of persons and object transistors before automatically initiating a close cycle. Another method frequently used to initiate the action of the door is a pressure mat installed in front of the entrance. The weight of a transitor upon the mat activates the door to an open position and holds it open as long as the pressure is maintained. A third method is from a request storage control such as in an elevator.
Although a sliding door operates in the plane of the opening, and thus avoids potential contact with the transitor due to the door's swinging action, the automatic closing of the door upon a person presents a hazard. For example, should the transitor pause and present no movement to the opening sensor the door will cycle closed. Even though the movement sensor is associated with a mat, with use and wear the pressure sensing features may no longer function, and thus the door will again cycle closed. A usual additional safety feature to provide against such unwanted closure and contact is the provision of one or more safety beams across the lower portion of the door opening which if interrupted by the presence of a transitor will cause the door to remain open. Despite the above safety features, the hazards of door closing contact upon a person or object still exists in the usual installation. This hazard is particularly applicable to elderly persons or those having ambulatory handicaps who may pause at the door entrance without interrupting the safety beams. An example would be a person using a walker who hesitates at the door. If the legs of the walker straddle the safety beam and the pressure mat is ineffective, the door will close upon the walker or the person at the end of the door delay. It is desirable, therefore, to provide automatic operating sliding doors with a safety feature that will prevent closing of the door or interrupt its closing cycle by the presence of an object or person in the plane of the door. It is desirable for such a safety feature to be effective and reliable, yet be inconspicuous, simple in operation, and relatively inexpensive. Applicant's invention meets these and other requirements.